


My Twin Sister Can't Be This Slutty!

by slotumn



Series: Cockslut Byleth [1]
Category: Fire Emblem: Fuukasetsugetsu | Fire Emblem: Three Houses
Genre: Accidental Incest, Alternate Universe - Modern Setting, Anal Fingering, Brother/Sister Incest, Cock Slut, Creampie, Dirty Talk, F/M, Female My Unit | Byleth, Glory Hole, Jealousy, Male My Unit | Byleth, My Unit | Byleth Twins, Sloppy Seconds, Slut Shaming, Spanking, Twincest, Vaginal Sex, fbyleth is a massive cockslut, including for her own brother, thats it thats the fic
Language: English
Status: Completed
Published: 2020-11-19
Updated: 2020-11-19
Packaged: 2021-03-10 06:49:07
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 1,187
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/27629099
Author URL: https://archiveofourown.org/users/slotumn/pseuds/slotumn
Summary: "I'm telling ya, pal. You gotta get some pussy and stop being so damn weird over that sister of yours."---Belzev is obsessed and overly protective over his twin sister's purity. Unknown to him, Beleth is a regular at the gloryhole Yuri and Balthus takes him to.
Relationships: Byleth/Byleth
Series: Cockslut Byleth [1]
Series URL: https://archiveofourown.org/series/2020129
Comments: 2
Kudos: 56
Collections: FE3H Kink Meme





	My Twin Sister Can't Be This Slutty!

**Author's Note:**

> For the [kink meme](https://3houseskinkmeme.dreamwidth.org/2082.html?style=site&thread=3356962). I'm really wilding out with the titles recently, huh. But anyway, all hail incest cockslut F!Byleth.

"I'm telling ya, pal. You gotta get some pussy and stop being so damn weird over that sister of yours."

Over the thin wall came a voice she recognized— Balthus, who had fucked her cunt and ass earlier with that long, thick cock of his, not knowing that she was the sister Belzev made him swear to never touch. 

"Yeah, seriously. Besides, how do you know that she's not already sleeping around behind your back? Especially when she's got those banger tits and ass." 

The next person to speak was Yuri, who no doubt earned a death glare from her brother, judging by the amused laughter he gave afterwards. 

She didn't need to hear his voice to know who the third man was, or what he must be thinking, looking at her ass and cunt hanging out of the wall— like a fucktoy, an inanimate piece of meat that didn't need the kind of care one would show a proper partner. 

Both of her holes were already sore from being fucked all evening, and there must have been ten, fifteen, maybe twenty tally marks on her ass, once for every time someone came in her; but her cunt was twitching and getting wet from the anticipation again, even when she knew who her next user would be.

 _Especially_ because she knew.

"...Can't believe I'm doing this," she heard her brother— her twin brother— mutter, as his footsteps approached, then stopped.

There were two fingers on her ass, poking tentatively, and she had to bite her lips to not giggle (as covering her mouth with her hands was impossible when her wrists were bound to her ankles). Oh, this was Zev, alright, she thought— the same Zev who was always more timid than she was when they were children, even though most people couldn't tell because they were equally expressionless. 

The same brother who now hated how other guys ogled her, pretending his obsession with her— specifically, her purity, her _innocence_ — was just "brotherly protectiveness," but she always knew better. 

It was more than jealousy, more than possessiveness; it was the instinctive threat an animal felt at having their mate stolen. 

"Sweet Sothis— twenty-four times? Who in the fuck would..."

He didn't know that she'd already fucked just about every man they knew, and then some.

Sylvain, who told her that he never knew that the weird stoic TA in one of his courses had such a "hot piece of ass" for a sister, as he triple-teamed her with Felix and Dedue. Ferdinand and Ashe, who both said they wanted to get to know her first, and ended up fucking her throat like it was the end of the world a week later. Seteth and Dimitri, who Zev sometimes confided in, over their shared "concerns" about their respective female family members and the (other) men who were after them. 

(Her own students were, surprisingly, something of an exception, most of them already being in a stable established relationship— but even then, Beleth gladly accepted the threesome offer from Claude and Lysithea, coaching her youngest student on the proper way to take cock until she passed out, and then Lorenz and Leonie, competing to see which one of them could make Mr. Prim and Proper come faster and harder.)

_Slap._

"Whore."

The sudden impact on her rear brought Beleth back to reality, alongside a fresh jolt of arousal. 

She couldn't help but exhale when something firm pressed against the entrance, then gasped when it slammed in all the way without a warning, extra cum splurting out of her cunt from the impact. 

"No, you're even _lower_ than a whore, aren't you," came something halfway between a pant and a growl, alongside yet another slap, this time on the other cheek. "You don't even take money for this shit, huh. Cheap fucking slut."

Oh— this was even better than she'd imagined, Beleth thought, cunt squeezing around her brother's cock. She swore she was already close, hearing such disgust and disdain and _arousal_ coming from her twin. 

After the next thrust, he shoved two fingers into her ass, knuckles deep, the cum inside acting as lubricant; she didn't try to hold back the moan when he spread his fingers and forced her to gape, but he didn't seem to recognize her voice. 

"You're pretty tight for a cumdump. Thought these would be looser, from getting knocked up and popping out a few kids."

_Slap, slap._

Alongside every thrust came a hard strike on her ass cheeks from his palms. His balls, hanging hot and heavy, hit her clit, too, giving just enough stimulation to push her into a climax; yet Zev didn't stop fucking her, the head of his cock mercilessly slamming into her cervix through the contractions. 

"Do people around you know?" he spat, breathing and thrusts growing more frantic. "Of course they already took turns with you, but do they know that you're such a _depraved cockslut_ that you come here to whore your holes out to strangers all night?"

It took all her sanity and self-control to not moan out his name right then and there— to hold herself from finding out what he would do upon finding out that the fucktoy he was releasing his frustrations and cum into was his pure, virginal twin sister. 

"...Guess even dirty sluts like you do something good for this world, though," he muttered, as his fingers and limp cock slid out. "Getting fucked so that my sister won't have to."

There was a pop of a pen cap opening, then the sensation of a felt tip on her ass as another tally mark was added. Beleth tensed up in an attempt to keep her brother's cum inside as much as possible, but that proved to be futile, as Yuri whistled and walked up, prodding her ass with his cock. 

"You sure you don't wanna use her ass? I'm not usually an anal guy, but you're really missing out if you don't try this one."

"It's fine," said Zev, voice now calm once more. "What time is it?"

"Almost ten," said Balthus. "Night's just getting started!"

"I'll be going home before twelve, if that's alright with you two."

Yuri sighed, roughly pushing in. "It's because of your sister, isn't it."

"Damn, even that pussy wasn't enough to make ya forget?"

"At this point, I'd say asking Zev to not think about his sister is like asking you to not chase MILFs."

Zev made the slightest grumbling noise, the one only his other half would recognize as embarassment. 

"I just don't want to make her worry, that's all."

"Sure, sure."

"You do you, chief!"

\---

A few hours later, Belzev stumbled into his apartment, flushed and reeking of alcohol as he rambled to his twin about how club he came back from had "too many filthy bastards who would take advantage of good girls like you without a second thought, so don't ever go to places like that, okay, sis?"

Beleth absentmindedly hummed something like an agreement, relishing the feeling of his cum inside her cunt and his head resting on her lap. 

**Author's Note:**

> Feel free to leave prompts/suggestions on my [CuriousCat](https://curiouscat.qa/slotumn)!  
>   
> [My twitter](https://twitter.com/slotumn?s=09)  
> 


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